The HTML above, without a !DOCTYPE declaration, causes IE6 to render in backward-compatible, regular run-of-the-mill IE mode. The background color applied to the HTML element is ignored, as are the position, left, top, height and width style declaration properties.

The HTML above has a !DOCTYPE declaration. IE6 is forced to render in standards-compliance mode. Notice that the background color applied to the HTML element covers the whole browser window. The BODY element renders as a positioned element. All the style declaration properties are valid. The BODY element, therefore, is only the yellow rectangle in the center of the window.